RARE Partnership Tackles Vapor Intrusion

EPA-led partnership brings scientists together to address the challenges of harmful vapors intruding into buildings.

Most threats to building occupants, such as fire, flood, hazardous spills, or structural damage, are dramatic and easy to identify. But while it may not be something you hear or see every day, vapor intrusion—the contamination of indoor air by harmful gases that migrate upward from the ground—also poses serious health risks. Recently, vapor intrusion has emerged as a major issue at hazardous waste sites nationwide as scientists have learned more about how volatile organic compounds and other gases migrate from buried wastes and contaminated soil or ground water.

The conditions that lead to vapor intrusion are similar to those that occur when radon gas enters a building, rising from soil through small cracks and gaps in the foundation. Instead of radon, however, vapor intrusion unfolds when harmful chemical compounds find their way into a building. One typical source, for example, is industrial degreasers, such as trichloroethylene (TCE), that have contaminated groundwater and migrated under buildings and homes.

EPA researchers and engineers have cultivated a collaborative research partnership to advance the scientific understanding of the complex set of conditions that can lead to vapor intrusion.

Researchers from EPA’s Office of Research and Development (ORD) teamed up with EPA Region 9 (the Pacific Southwest) colleagues to evaluate several new practical methods to assess the pathway that leads to vapor intrusion in buildings. Supported with a RARE grant (see RARE Partnerships), they tested and compared three different methods that might provide ways to investigate vapor intrusion in buildings: (1) using radon sample data as a surrogate for determining vapor intrusion; (2) using building pressure differential to assess the potential for vapor intrusion; and (3) using a sampling device that soaks up air particles for longer, time-integrated measurements (from three days to two weeks) of indoor air. The research team conducted the fieldwork for the project at a former military housing complex at the Naval Air Station Moffett Field Superfund Site in California.

They found that the third approach was the most promising.

The team’s evaluations of the assessment methods will provide project managers nationwide with important information that they can incorporate for improving vapor intrusion indoor air investigations in a practical, cost-effective, and health-protective manner.

To ensure these outcomes reach concerned community leaders and others faced with addressing the challenges of vapor intrusion, the Agency plans and leads workshops and other public events. A Vapor Intrusion Workshop is planned for 2012.

What EPA researchers are learning will provide information necessary to better assess and measure vapor intrusion, helping the Agency to protect human health.